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Medium, CVSS 5.9amended

Fiber: CORS wildcard origins matched without a dot boundary, allowing credentialed cross-origin reads

CVE-2026-119285GHSA-g5jq-qmqr-qrwf

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/gofiber/fiber/v2 2.52.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N
EPSS
  • CVE-2026-119285: 0.13% estimated exploitation activity in the next 30 days; percentile 2.53 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary In v2.52.1 and v2.52.2 the CORS middleware matched a wildcard origin such as `https://*.example.com` by suffix only, without a dot boundary and without comparing the scheme. Any origin whose host ends with the base domain, for example `https://evil-example.com` or `http://notexample.com`, was reflected in `Access-Control-Allow-Origin`, together with `Access-Control-Allow-Credentials: true` when `AllowCredentials` is enabled. v2.52.3 replaced the matcher (#2915) and is not affected. The report was filed against v2.52.15, where the dot boundary holds; see "Other versions" below.

Details v2.52.1 introduced `validateDomain` in `middleware/cors/utils.go` (f0cd3b44, part of the fix for GHSA-fmg4-x8pw-hjhg). It strips scheme and port from both sides and then checks only the suffix, with `trimmedPattern = "example.com"`, so the character before the suffix is never checked: ```go if strings.HasPrefix(normalizedPattern, "*.") { trimmedPattern := normalizedPattern[2:] if…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from osv record GHSA-g5jq-qmqr-qrwf

  2. Revision 1 · created ·

    Published from ghsa record GHSA-g5jq-qmqr-qrwf

Agent brief

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# Patch Next advisory brief: CVE-2026-119285

Advisory: Fiber: CORS wildcard origins matched without a dot boundary, allowing credentialed cross-origin reads
IDs: CVE-2026-119285, GHSA-g5jq-qmqr-qrwf
Record: https://patchnext.com/advisories/cve-2026-119285 (revision 2, source checked 31 Oct 2026, 06:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/gofiber/fiber/v2 2.52.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/gofiber/fiber/v2: affected >= 2.52.1, < 2.52.3; fixed in 2.52.3

## Suggested inspection (read-only)
- Go github.com/gofiber/fiber/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/gofiber/fiber/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-g5jq-qmqr-qrwf (GitHub-reviewed advisory GHSA-g5jq-qmqr-qrwf lists affected ranges: Go github.com/gofiber/fiber/v2 >=2.52.1 <=2.52.2)
- Verified: https://osv.dev/vulnerability/GHSA-g5jq-qmqr-qrwf (OSV record GHSA-g5jq-qmqr-qrwf lists affected ranges: Go github.com/gofiber/fiber/v2 >=2.52.1 <2.52.3 (fixed))

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